A time-division multiple-access (TDMA) link offers the possibility to a network composed of earth stations—also called sites—to transmit at a regular frequency their respective signals. The sites share a single-carrier link communication, they send at regular time interval an information packet that is time-shifted from all the other packets, to prevent information collision. Although the link is shared, the communication network can operate with no packet collision, because the sites are well synchronized and there is a reservation algorithm assigning the traffic.
Thus one of the advantages of a network based on a TDMA link is to provide a dedicated bandwidth to each site of the network without the problems associated with information packet collisions and at the same time to utilize almost all the bandwidth resources of the link therefore offering an efficient system. The dedicated bandwidth can be, for example, used to transmit voice communication, a continuous stream of traffic that requires fixed and limited time delays.
However, it could be advantageous for some of these sites, if not for all sites of the network, to have additionally access, from time to time, to an additional portion of the link to send in burst mode information coming from other media, such as emails, file transfers, etc. In other words, to have access, additionally to a dedicated bandwidth, to a dynamic bandwidth that could be shared between some or all of the sites.
It would also be an advantage if a network could offer both bandwidths (dedicated and dynamically assigned) and manage this network automatically without the need of an external controller because those controllers are generally costly. Therefore there is a need for a communication system that is more flexible but still very efficient, and that is in the same time a simpler and cheaper solution then available systems.